Plug and grounding means



July 17, 1962 w. D. HALL 3,045,201

PLUG AND GROUNDING MEANS Filed Oct. 8, 1959 FIG. I.

William D, Hall United States Patent O 3,045,201 PLUG AND GROUNDING MEANS William D. Hall, 5112 Westpath Court, Montgomery County, Md. Filed Oct. 8, 1959, Ser. No. 845,119 4 Claims. (Cl. 339-14) This invention relates toplugs that have grounding means and has for its main object the provision of a third wire grounding means in devices using certain types of plugs.

Air conditioners have frequently employed thermostats. For air conditioners which did not have thermostats as original equipment, for a number of years there have been available on the market thermostats which could be attached to the air conditioner. One form of such thermostats included a series plug and socket which was inserted in the wall and the air conditioner was plugged into the socket of the series plug. However, the arrangements were of such character that it was impossible to add or provide for the third wire grounding prong on the plug of the air conditioner. The present invention overcomes this difficulty and provides for grounding of the third wire prong.

The same thermostat that is used on air conditioners is often used for other articles such as electric fans where the third prong is not needed, and one object of the present invention is to provide an arrangement whereby the plug on the end of the thermostat has universal. application. It can be used to receive an air conditioner plug with three prongs irrespective whether the wall socket has a third prong or not. If it has, provision is employed to use it. Moreover, the thermostat and series plug of this invention may receive a plug with only two prongs even though the wall socket may have provision to receive three. If the plug of the air conditioner should have three prongs but the wall socket only has provision to receive two, here again the device is applicable.

Other objects and advantages of the invention will appear as this description proceeds.

In carrying out the aforesaid objects, said series plug 'is of rectangular shape but not thick enough to interfere with the normal position of the third prong on the plug of the air conditioner. In addition to the series plug there is a pin with a socket on the rear end which is separate from the plug and which may be inserted in the wall socket and will receive the third prong of the plug of the air conditioner.

In the drawings:

FIGURE 1 is a side view of the invention.

FIGURE 2 is a top detailed view of the invention.

FIGURE 3 is a further detailed view of the invention.

FIGURE 4 is a view partly in cross-section of the supplemental plug used in connection with this invention.

In the drawings a three-wire electric cord leading to an air conditioner is fed by a three-prong plug 11. As is customary on air conditioners such a plug has two flat blades 12 and 13 for transmitting the electriccurrent and a third prong 14 acting as a grounding pin. The wall socket 15 has the usual sockets 16 and 17 for the blades and a third socket 18 for the grounding pin. A series plug 19 has blades 20 and 21 respectively adapted to be inserted in sockets 16 and 17. This plug also has sockets 22 and 23 to receive the blades 12 and 13 of the plug 11. Blade 21 is electrically connected directly to socket 22. Blade 20, however, connects to wire 24;

and socket 23 connects to wire 25 and these two wires pass to the thermostat 26 which may be mounted on the air conditioner. is inserted in the wall socket 15 and the plug 11 is in serted in the rear end of the series plug 19, the thermostat 26 is directly in series with the air conditioner. The apparatus shown in FIGURE 4 includes a socket element 27 for receiving the pin 14 and a prong 28 for insertion in the third socket 18 of the wall socket 15. By making the series plug 19 relatively thin it does not interfere with the third prong 14 on the plug 11, whereby the socket member 27 may be placed on that prong and also inserted in socket 18 for grounding purposes. In event the wall plug 15 does not have provision for a third socket 18, the apparatus can still be used without mutilating the'plug 11 of the air conditioner, by simply omitting the member 27, 28 which is in a separate piece from the series plug 19. In event the thermostat is used to control a fan or other appliance which has a plug 11 with only two instead of three prongs, the member 27, 28 may be discarded and the plug 19 used irrespective of whether the wall outlet has two or three socket elements.

I claim to have invented:

1. In combination, a plug with a generally rectangular cross-section extending from its front to its rear end with two parallel blades which are parallel to the short sides of the rectangle and which project out of the front end of the plug, said blades being adapted to be inserted into the two live socket elements of a wall socket and the rectangle being so narrow as not to cover the ground socket of the wall socket, a three prong plug having two current carrying blades and a grounding prong, the firstnamed plug having a rear end that has two socket elements for receiving the two current-carrying blades of the three prong plug, and a member having a socket on its rear end for receiving the grounding prong of said three prong plug and having a prong on its front end for insertion into the grounding socket element of the wall socket.

2. The combination of claim 1 in which said member is in a separate piece from said first named plug and is unattached thereto.

3. The combination of claim 1 in which the first-named plug is a series plug that has a line cord proceeding therefrom.

4. The combination of claim 1 in which the first-named plug is a series plug so thin that it does not interfere with a third prong on the plug which it is adapted to receive at its rear end, said member being in a separate piece from the first-named plug and unattached thereto whereby it may be inserted in the wall socket and also receive the third prong of the three-prong plug.

' References Cited in the file of this patent UNITED STATES PATENTS Germany Feb. 26, 1951 As a result, when the series plug 19. 

